HTML disappears!

I’m using wordpress for all the text, but want to paste youtube videos via HTML into my code (unless there’s a better way to get them to show up visually)

If I switch between HTML and Visual Editor, all my HTML is lost. I want to add a video, but still edit my text in the visual editor.

Can this be done? Is there a way around this? Should I stick only to HTML for everything (this is why I switched to wordpress in the first place.)

Please help.